7 - Facial growth 2 Flashcards
How does the mandible form?
Intramembranous ossification
How does the maxilla form?
Intramembranous ossification
Describe the neonatal face.
- face is smaller in comparison to the head
- eyes are large
- ears low set
- forehead is upright and bulbous
- short nose
How does the skull develop?
- sutures
- synchondroses
- surface deposition
What is a suture?
- fibrous joint between intramembranous bone
- band of connective tissue that has osteogenic cells which provide new bone growth
- growth happens in reaction to other structures applying force the bone and pulling the suture apart
- when growth is complete the sutures fuse
What are synchondroses?
- cartilaginous plate pushes apart in two directions
- found in midline
- exist between ethmoid, sphenoid and occipital bones
- cartilage based growth occurs by bones on either side moving away
- new cartilage is formed in the centre of the synchondrosis whilst the outer cartilage turns to bone
What is surface deposition?
- new bone is deposited on the periosteum of existing bone
- bones maintain shape by resorption occurring on the opposite surface
- known as remodelling
- the change in position is known as drift
How does the vault grow?
- occurs until age 7, rate of growth greatest until age 3
- growth occurs at the sutures (intramembranous ossification) and via surface deposition
- surface deposition causes the vault to increase in size radially
How does the cranial base grow?
- endochondral ossification and surface remodelling
- half the growth is completed by age 3 but continues until age 20
What are the different synchondroses of the skull?
- spheno-ethmoidal
- spheno-occipital
When does the spheno-ethmoidal synchondrosis fuse?
7 years
When does the spheno-occipital synchondrosis fuse?
- CLOSES around 13-15 in females and 15-17 in males
- FUSES at around 20 years
How does cranial base growth impact orthodontics?
- due to the anterior cranial base finishing growth at age 7, it can be used to superimpose lateral cephs to assess growth in other areas
- the angle and size of the cranial base affects the maxillary and mandibular relationship
Describe the growth of the maxilla.
- follows neural growth pattern
- articulates with the anterior cranial base
- cranial base displaces displaces maxilla downwards and forwards
- this creates space for maxillary tuberosities and eruption of molar teeth
- sutural growth occurs at zygomatic and frontal bones, as well as the mid-palatine suture
- surface deposition on hard palate, alveolar process and nasal cavity
Describe the growth of the mandible.
- downwards and forwards
- growth occurs at condylar cartilage and surface remodelling
- deposition of bone mainly posterior and laterally
- resorption of bone mainly at anterior and lingual surfaces
- height of ramus and length of dental arches increased
When does the mandible stop growing?
- growth spurt during puberty
- stops at 17 years in females and 19 years in males
When does the maxilla stop growing?
- follows neural growth pattern
- age 7 growth slows
- age 12 growth stops
When does jaw width growth slow?
- before pubertal growth spurt
- ie after canines erupt the aesthetics won’t change naturally
When does jaw length growth slow?
- 14-15 in females
- 18 in males
When does jaw height growth slow?
- 17-18 in females
- into 20s for males
How can you predict facial growth?
- previous growth patterns
- height in relation to chronological age along with sex
When can rapid maxillary expansion be used?
Before the mid palatal suture closes at age 15
When can headgear be used?
On class III patients before age 10
What does a forward growth rotation result in?
Short face
What does a backwards growth rotation result in?
Long face
Describe adult facial growth.
- continues slowly throughout adult life
- increased overall length of nose and chin
- lips become thinner and more retrusive
What can be used to measure facial growth?
- casts of face
- cephalometry
- 3D laser scanning
- 3D photogrammetry (orthognathic)
